Genomic alterations and clinical correlations of Chinese patients with hepatoid adenocarcinoma of the stomach/alpha-fetoprotein gastric cancer.

Abstract

e13514 Background: Hepatoid adenocarcinoma of stomach (HAS) is a rare subtype of gastric cancer (GC) with poor prognosis due to frequent liver metastasis. HAS, recognized as an extrahepatic cancer that resembles hepatocellular carcinoma (HCC), is characterized by solid sheet-like growth structures with hepatoid differentiation and excessive production of alpha-fetoprotein (AFP). This HAS subtype of GC (AFPGC) is genetically distinct compared to other common GC but requires more evidences for better characterization. Methods: Formalin-fixed, paraffin-embedded (FFPE) tumor tissues were collected from 25 HAS and 9 AFPGC patients at Zhongshan Hospital from July 2013 to August 2017 for whole exome sequencing (WES) test. The testing was carried out by a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Results: Our cohort included 25 males and 9 females who had undergone surgical treatment. The 25 HAS patients had a median age of 66.5 years (range 48-82) and the 9 AFPGC patients had a median age of 64 years (range 52-76). Patients with AFP>20 had a significantly better overall survival (OS) compared with patients with AFP≤20. The most frequently mutated genes were TP53 (44%), TTN (44%), and MUC19 (30%) in HAS tumor samples and CDC27 (44%), NKX2-3 (44%), and TTN (44%) in AFPGC samples. Patients with URI1 or POP4 alterations had a significantly poorer OS than patients without those genes mutations (7.6 months vs. 19.8 months, p = 0.016, and 10.9 months vs. 19.7 months, p = 0.038, respectively). However, patients with SPTA1 alterations had a significantly better OS compared to patients without SPTA1 alterations (27.6 months vs. 15.8 months, p = 0.042). Patients with higher tumor mutational burden (TMB) (≥3.9 muts/Mb) had a significantly better OS compared with patients with lower TMB (<3.9 muts/Mb), which indicated TMB may be an independent prognostic factor (HR: 0.032, 95%CI: 0.003-0.33, p = 0.004). Conclusions: Our study revealed the genomic profile of HAS/AFPGC patients. The most frequently mutated genes in HAS and AFPGC were different, which helps to better characterize these tumors. AFP and TMB may be potential biomarkers for predicting patients’ prognosis.